1. Technical Field
The present invention relates to a magneto generator for power generation utilizing electromagnetic induction between magnet and armature winding by rotating a flywheel.
2. Background Art
FIGS. 6 and 7 show a rotor of a flywheel-type magneto generator according to a prior art disclosed in the Japanese Patent Publication (examined) No. 81437/1994. FIG. 6 is a plan view of the rotor, and FIG. 7 is a sectional view taken along the line VIIxe2x80x94VII of FIG. 6. FIG. 8 shows a guard ring of the flywheel-type magneto generator according to another prior art disclosed in the Japanese Patent Publication (examined) No. 81437/1994. In these drawings, reference numeral 1 is a bowl-shaped flywheel formed by a circumferential wall portion and a side wall on one end side of the circumferential wall portion. Numeral 2 is plural magnets 2 continuously arranged in the circumferential direction on the inside of the circumferential wall portion of the flywheel 1. Numeral 3 is a cylindrical guard ring arranged annularly to fit tightly inside the magnets 2, and the guard ring 3 holds the magnets 2. Numeral 4 is a resin with which both side portions of the magnets 2 and spaces between end portions of the respective magnets 2 are filled to fix the magnets 2 and the guard ring 3 integrally onto the flywheel 1. Numeral 5 is a boss portion mounted on a rotary shaft (not shown in the drawings) fixed to the center of the side wall portion of the flywheel 1.
In the rotor of above construction, the guard ring 3 is arranged for the purpose of preventing the magnets 2 from being damaged when the magnets 2 arranged on the circumferential wall portion of the flywheel 1 collide with other object due to magnetic force at the time of handling the rotor. Drawing a steel plate has formed the guard ring 3.
In the rotor of the mentioned conventional magneto generator, each of the magnets 2 has a polarity which is reverse polarity of the neighboring magnets 2 in order to generate an electric power. The guard ring 3 is composed of a carbon steel plate of high magnetic permeability. The guard ring 3 has continuous annular construction as shown in FIG. 8. Therefore, when the rotor rotates along the outer circumference of a magneto coil (not shown), a magnetic flux does not effectively flow from the magnets 2 to an iron core of the magneto coil. But a part of the magnetic flux flows to the neighboring magnets 2 through the guard ring 3. This causes a problem of deterioration in power generation efficiency.
It is certainly possible to form the guard ring 3 of a material of smaller magnetic permeability, for example, a non-magnetic steel plate of stainless steel or the like, and it is also possible to improve power generation efficiency. But, this causes another problem that the material cost is expensive.
The present invention was made to resolve the above-discussed problems and has an object of obtaining a magneto generator in which a magnetic flux from magnets effectively flows to an iron core of a magneto coil at the time of rotating a rotor of the magneto generator, thereby generating an electric power efficiently.
A magneto generator according to the invention comprises a bowl-shaped flywheel formed by a circumferential wall portion and a side wall portion on one end side of the mentioned circumferential wall portion, plural magnets arranged on an inner peripheral surface of the mentioned flywheel, a cylindrical guard ring being in close contact with inside of the plural magnets, and a magneto coil arranged in the flywheel so as to oppose to the magnets in order to generate an electric power utilizing electromagnetic induction between the magneto coil and the magnets, wherein the mentioned guard ring has opening portions at positions opposing to adjacent two end portions of the mentioned magnets neighboring to each other. As a result of such construction, even when the guard ring is composed of a carbon steel plate of high magnetic permeability, it is possible to prevent a part of magnetic flux from flowing into the neighboring magnets through the guard ring at the time of generating an electric power. Thus, it is possible to improve power generation efficiency.
In the magneto generator according to the invention, it is preferable that the opening portions of the guard ring are arranged at every boundary portion of the neighboring magnets.
Another magneto generator according to the invention comprises a bowl-shaped flywheel formed by a circumferential wall portion and a side wall portion on one end side of the mentioned circumferential wall portion, plural magnets arranged on an inner peripheral surface of the mentioned flywheel and polarized into plural poles, a cylindrical guard ring being in close contact with inside of the plural magnets, and a magneto coil arranged in the flywheel so as to oppose to the magnets in order to generate an electric power utilizing electromagnetic induction between the magneto coil and the magnets, wherein the mentioned guard ring has opening portions at positions opposing to adjacent two end portions of the mentioned magnets neighboring to each other and at positions opposing to magnetic pole boundary portions of the mentioned magnets.
In the magneto generator according to the invention, it is preferable that the opening portions of the guard ring are arranged at every boundary portion of the neighboring magnets and for every magnetic pole boundary portion of the magnets. As a result, it is possible to improve power generation efficiency.
In the magneto generator according to the invention, it is preferable that the opening portions of the guard ring are filled with a resin, the mentioned resin filling a space between the guard ring and the flywheel, and the magnets are embedded in the resin. As a result, the magnets located at the opening portions are not exposed, and it is possible to guard the magnets from being damaged due to any shock.
Other objects, features and advantages of the invention will become apparent in the course of the following description.